Verizon has asked the FCC to relieve the service provider of its obligations to upgrade and replace SS7 signaling equipment, illustrating another sign of the telco’s network transition from legacy TDM to IP.

In an FCC filing (PDF), the service provider said it is seeking limited relief from the FCC’s rules for three main situations:

Legacy SS7 elements: Verizon wants to be relieved of an FCC requirement to upgrade and replace legacy SS7 network elements in order to generate and pass the charge number (CN) when it differs from calling party number (CPN).

Legacy multi-frequency equipment replacements: This is signaling equipment that Verizon would have to replace in order to signal CN or CPN.

VoIP traffic: Verizon said this relates to limited situations involving VoIP traffic, including when, as an intermediate carrier, the telco receives traffic with improperly formatted or unverifiable CPN or CN.

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This request follows a petition Verizon made in 2012 where the telco said that the costs of upgrading or replacing the network elements to comply with the FCC’s rules “as written would far outweigh the benefits,” adding that “these network elements, over time, would phase out of the network.”

Verizon has continued to shut down more of its SS7 signaling switches as more of its customers migrate from TDM to IP-based services. In 2012, Verizon identified 10 SS7 switches it would have to replace to CN if different from CPN.

The service provider currently only operates three of those switches on its network, and it has plans to remove one of them.

“With these and other evolutions in the network, and as more and more traffic moves to IP interconnections, the scope of the relief we seek is even more limited than it was when we filed the Petition,” Verizon said.

Verizon said that it when it has to act as an intermediate carrier, it still receives improper or unverifiable CN and CPN information on VoIP traffic because the telecom industry has not implemented call signaling standards. Despite that, the telco added that VoIP traffic exchanges have continued to drop.

In order to minimize issues with VoIP traffic exchange, Verizon has developed and implemented an IP interconnection platform for VoIP traffic that’s similar to the ATIS SIP Forum Task Force’s SIPconnect 2.0 specifications.

Verizon said that “while that initiative recommended signaling standards for VoIP traffic, each provider has discretion whether and to what to extent to adopt and implement the recommendations.”

Since Verizon continues to see incorrect CN and CPN on traffic it receives, the service provider created a process to improve the signaling quality on the traffic other providers send them.

The service provider said that “this process has reduced the frequency with which these problems occur,” adding that “the onus to improve call signaling is on the party that is sending us the traffic.”

“Verizon was not the only provider to seek a waiver, and no one opposed our request based on the need for one,” Verizon said in its FCC filing. “The limited opposition we received in 2012 focused on the breadth of our request. But as we explained then, our Petition seeks only limited relief, and it has become even more limited as legacy equipment phases out and as we work to improve call quality for VoIP traffic.”

Similar to earlier Verizon’s request to discontinue collect calling, this latest request reflects the ongoing reality that end-users are continually migrating off of legacy TDM voice to some form of IP-based wireline and wireless voice service.